If the plates of a capacitor are separated and a thin conductor is placed between the plates and does not touch either plate the overall capacitance is equal to the capacitance created by the distance between each plate and the thin conductor. As seen in FIG. 1, if a capacitor 12 is placed in series with an inductor 14 and a resistor 16 and the circuit is caused to resonance with an alternating current the current is the same in all parts of the circuit. A thin conductor placed between the separated plates of the capacitor in an RLC circuit acts just like a conductor in the circuit separated by two separate capacitors in an RLC circuit. Since the thin conductor acts like another conductor in the circuit separated by two separate capacitors, it is now part of a new RLC circuit and a current will be induced on it as if it was just another conductor in the resonating circuit.
When the reactance of the inductor is equal to the reactance of the capacitors in the circuit the circuit will resonate at a natural frequency and there is only resistance in the circuit. This resistance can be varied externally. Since all the current is uniform in a resonating circuit the externally varied current will vary the current induced in the thin conductor between the plates of the capacitor because the thin conductor is now part of the circuit. This concept can be demonstrated experimentally by placing a fine wire 22, separated by air space, between two conductors 24,26 as shown in FIG. 2. The conductors are then placed in series with an inductor 28 and caused to resonate using a signal generator 30 connected in series. It can then be shown using an oscilloscope 32 that at resonance the current in the isolated thin wire is the same as any other point in the circuit and its amplitude can be controlled externally by varying the signal generator current output.